Centralized traffic controlling system for railroads



Aug. 28, 1945. T. J. JUDGE 2,333,303

CEQTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROAQS Filed Feb. 26, 1942 5 Sheets-Sheet 1' S XEG NQ. J

3W bk Tu Y M ATTORNEY T. JUDGE 2,383,803

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Aug. 28, 1945.

' Filed Feb. 26, 1942 5 Sheets- Sheet 2' v n m w on v2 3. TV Tu FIGQTZ.

Aug. 28, 1945. T. J. JUDGE 3 CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Feb. 26, 1942 s Sheets-Sheet3 it t a [is r E 3 AKTTORNEY Patented Aug. 28, 1945 UNITED CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General N. Y.

Railway Signal Company, Rochester,

Application February 26, 1942, Serial No. 432,428

11 Claims.

The present invention relates to centralized trafiic controlling systemsand more particularly to a centralized trafiic controlling system of the unit line wire type in which a control and an indication may be transmitted over the same line circuit contemporaneously.

It is well understood by those skilled in the art of railway signalling that the cost of line wires is an important factor in any centralized traffic controlling system and that for this reason the number of linewires should be kept at a minimum. It is common practice to use the same line wire for transmitting controls in one direction and transmitting indications in the other direction at difierent times, in accordance with the present invention, however, it is proposed to transmit such controls and indicationsover the same line circuit by allotting the line circuit alternately for transmitting controls and indications at such a rapid rate that slow acting relays will manifest continuous reception of a control or an indication in spite of its intermittent interruption. In other words, it is proposed to transmit such a control and indication contemporaneously over a single circuit.

In view of the above and other considerations it is proposed, in accordance with the present invention, to employ double-throw contacts at a central office and at a field station each of which alternately connect that end of the line circuit to a control source of current or an indication relay at the oflice or to an indication source of current or a control relay at the field station, these double-throw contacts being operated at different rates such that control circuits and indication circuits are established intermittently at substantially the beat frequency of such rates. In the specific form of the invention illustrated two line circuits of the construction described are employed. I

Other objects, purposes and characteristic features of the present invention will in part be obvious from the drawings and will in part be understood from the following specification when considered in the light of the accompanying drawings, of which:

Fig. 1A and Fig. 1B conventionally illustrate a system of centralized traffic control and indication embodying the present invention; and

. Fig.2 illustrates graphically the operation of the two double-throw contacts as well as graphically showing the circuits intermittently established thereby.

illustrated including a track switch SW operated by a switch machine SM,,the position and locked condition of which track switch and switch machine is manifested by a switch indication relay WP. Switch indication correspondence relays NWP and RWP which when energized manifest that the switch control relay WZ and switch indication relay WP assumecorresponding normal and reverse positions, respectively. This track switch SW is provided with. the usual detector track circuit isolated from adjacent track circuits by insulating joints 9, and including a track battery B and a track relay T. The signals 1 and IA govern the movement of trafiic from east to west, that is, from right to left into the main track and side track, respectively, of the passing siding PS, whereas the signals 2 and 2A govern the movement of east-bound traffic off of the main track and the side track of the passing siding, respectively. These signals I, IA, 2 and 2A may be of any well known construction, such as semaphore signals, multiple unit light signals, or searchlight type signals, and for convenience only semaphore signals have been conventionally illustrated. A signal-at-stoprelay M has been illustrated, this relay M being controlled by contacts l6, l1, l8 and IQ of the signals IA, l, 2A and 2, respectively, and beingenergized when all of these signals assume the stop position or condition as is evident from these closed contacts with the signals at stop. These signals are controlled in accordance with traflic conditions in advance and by the signal control relay GZ, whereas the switch machine SM is controlled by a switch control relay WZ.

Referring now to the central office shown in Fig. 1A a miniature track layout including a miniature' representation of the passing siding PS has been illustrated by the miniature passing siding ps. This miniature passing siding 'ps has associated therewith a track occupancy indicating lamp TE which when illuminated manifests that the detector track circuit at the field station shown in Fig. 1B is occupied. Some other well known form of indicator may of course be used in place of each of the several indicating lamps shown. The miniature track layout is .also provided with indicating lamps or other suitable indicators OCE, GLE and GE. Of these indicators n Structura-Referring to Fig. IE it will be seen the-indicator OCE when lighted manifests that the track switch SW and the track switch control lever SlVLL assume out of correspondence positions. The electric lock indicator GLE when rendered active manifests that the signal lever SGL is assuming a clear position and/or an indiand switch indication are transmitted includes.

a line wire WZ-WK and a common return wire;

C, whereas the line circuit over which: signal: controls, signal indications, and track occupancy i'n-fi dications are transmitted includes a line wire GZ--GKTK and the same common return wire,

C. The central oflice end of these line wires WZWK and GZGK-TK are connected to double-throw contacts I and- 1 2', whereas the opposite ends of these line wires are connectedto double-throw contacts II and [3. The double-throw contacts t0 and I2 are attimes intermittently operated. to their opposite p'ositions alternately by acoder 156T operating at a rate to. repeatedly pick up these: contacts I 0 and I2: seventy-"live timesper minute, whereasflt'he double-throw contacts lland; is are similarly intermittently operated-by a coder IZOCT which operates these contacts H and I3 alternately to their two extreme positions one hundred twenty times per minute. These coders TBC'I" and IZBCT may be of any Well known construction and preferably arecprovidedwith interrupter contacts. M: and t5, respectively, for causing intermittent operation of these coders when-en'- ergy is applied to: the back stationary contacts associated'with thesemovable-contact l4 and i5". Allof these double-throw contact I IJ,1 l I, I2 and l-3 normally assume their deenergized position in which they connect their respective: line wires to relays, these contacts when. in .their raisedor attracted position-connecting their respective line wires to a source of currentiwhi-ch i-s controllable by manually operable leversin the office and by automatically operated contacts at the fieldstation to at times applyenergy to the front points of these double-throw contacts. Instead of employing polar-neutral relays to detectpresence and polarity of currenttransmitted through. a line circuit a=two-po'sition magstick relay WKS, and a neutral relay WK have been connected to the back point of the doublethrow contact J0 at the 'ofllce. g

I his mag-stickr'elay WKS is a polar relay which remains in the position towhich it was last operated, which polar mag-stick relay WKS when assuming either its positive or its negative position connecting the relay WK in multiple with the-winding ofthis relay WKS, so that the relay WK may manifest whether or not current is being received and if so whether this current is continuous or intermittent. This ralay WK is provided with two windings preferably having their turns arranged oppositely and selected by a polar contact 54 of the relay WKS. From this it is apparent that pole changing of the current applied to the relayWK'S will cause no pole changing of the magnetic flux in the core of the relay WK. Each of. the. other double-throw contact H, I 2' and I3 when in their retracted positionare connectedto similar mag-stick relays and neutral relays. These mak-stick relays for the double-throw contacts I 1, l2 and 13 have been designated WCS, 'IGKS- and GCS, respectively, whereastheir associated neutral relays have been designatedWC TGKand GC, respec tively. It may be pointed out that the relays WKS and WK are employed for receiving switch control indications at the oflice, whereas the elays TGKS and TGK are employed to receive both signal clear indications and track occupancy indications. Also, the relays WCS and WCarQemployed to control the switch control relay WZg, whereas the relays; GCS and G0 are employed to control the signal control" elay GZ. Since the neutral relays WK, TGK, WC and GC are quick acting relays and follow the impulses 1thatia're transmitted'over the line circuits, and

since continuous indications and controls are desired to be, manifested slow dropping repeater relays have been provided for these relays WK, TGK, WC and GC and these slow dropping reall of the relays except the witch control relay WZ are deenergized as are also the indicators 12E, OCE-,;GLE and. GE. In order to simplify the circuitsqsymb'olsl indicating (-1-), or C have-been applied to=the starting point. and the endingpOin-t; of. each c'ircu-itxto designate. the terminal (-1-), the terminal" (.-)",r or the common return wire: 0 to-which these points of the circuits are: connected. In order to complete these circu-itsl an office batteryBO provided. with. a terminal and. as terminaland having its mid-point connected to the common return wire C has. beenv illustrated... At the: field station a similarsource of currentv or battery BF has been illustrated which has" been provided with a terminal a terminal and. which has its mid-point connected to, the common return wire C, Asalready pointed out the switch control relay WZ (Fig. 1B) is; normally energized, it being energized through a stick circuit including the polar contact 20-, a stick contact 21 and; the back contact 22 or the relay WCP; Although it hasbeen statedthat the track switch SW is at the end of a. passing siding it should be understood. that. it may within thezscope of the present invention be located at a turn-out. In order to get a better understanding or the system, its mode of operation and the functions which it performs it. is believed desirable to now consider the operation of the system.

Ope ration Let usassume that there isan east-bound train on the main track of the: passing siding PS, or otherportion of. the railroad approaching the switch; SW, and that itis desired to-clear the signal 2 to allow this train to proceed over the track switch SW; Since the'track: switch already assumes its-main, track position it will be unnecessary to, operate the switch control leverSML. In order, however, to cause clearing of the signal, 2. it. will benecessary to operate the signal lever SGL to its east-bound, namely, its upper position. The operation of the lever SGL to its upper position causesclosure of an energizing circuitfor. the coder 15GB which may be traced from the terminal (-1-), through the contact 25 ofthe lever SGL andthrough interrupter contact [4 and the windingof the coder TEC'I'. This will causethe coder TECT to. intermittently pick up and drop its contacts 0 and [2. at the rate of substantially seventy-five times per minute. In-

termittent closure of front contact I 0. of coder T causes intermittent picking upof relay WC and the continuous picking up of relay WCP. This results in closure, of a different. energizing circuit, namely, a' pick-up circuit, instead of the normal stick circuit for the relay WZ which produces no change in the position assumed by the relay WZ and the track switch SW.

' Intermittent closure of the front contact |2 of this coder I5CT causes current of positive polarity to flow from the terminal through the contact 26 of the signal lever SGL, through the back contact 2'! of the out-of-correspondence relay OCR, through front contact |2 of the coder CT, through. line wire GZ-GKTK, through back contact l3 of the coder |2UCT, and through windings of the relay GCS and GC in multiple to the common return wire C connected to the mid-point of the office battery B0. The intermittent closure of this circuit causes the ma stick relay GCS to assume the proper polar position and causes intermittent picking up of the relay G'C. Intermittent picking up of the neutral line relay GC causes intermittent closure of its front contact 29 and intermittent energization of the slow dropping line repeater relay GCP. This intermittent energization of line repeater relay GCP, since it is sufliciently slow dropping so as not to drop between the impulses of 0111? rent received, causes its'front contact 30 to be maintained closed continuously. Since the contact 3| of the mag-stick relay GCS assumes its right-hand position continuously the signal control relay GZ will have its positive polarity energizing circuit including these contacts'3l and 3|] continuously closed, so that this signal control relay GZ is'continuo'usly energized to its right ance with traffic conditions in advance. Had the signal indication relay 62 been energized for setting up west-bound traffic, that is, energized to its left-handpositionfa different signal clearing circuit'3'l, including a contact 39 of the switch repeater relay NWP, would have been closed.

The clearing of the signal 2, as for reasons just pointed out; causes deenergizati'on of the signal-at-stop relay M, for reasons heretofore pointed out, as a result of which its back contact 40 closes anenergizing circuit for the coder lzliCT, causing intermittent operation of this coder at the 120 actuations per minute rate to cause thecontact l3 to belifted and dropped substantially 120 times per minute. Also, the dropping f the signal-at-stop relay M causes, by the closure of its back contact 4|, current of positive polarity to intermittently flow from the terminal through back contact 4| of relay M, through front contact I3 of coder l2llCT, through back contact I2 of coder-150T, through the winding ofthe mag-stick relay TGKS, to common return wire C, and also through a multiple branch including the polar contact 42 of the relay TGKS assuming its right-hand position and the lower winding of the neutral relay TGK from whence the current flows through the common return wire C, which is connected to the midpoint'of the field battery BF;

' The intermittent"energization of the neutral relay TGK' causes its front contact 44 to intermittently energize the slow dropping line repeater relay TGKP, :and' since this relay TGKP is sufficiently slow'dropping so as not to drop between impulses this relay TGKP remains,in its energized position continuously, during intermittent picking up of relay TGK, and closes its front con tacts 45"and 46 continuously. The closed front contact 45-merely-closes a multiple circuit for the indicating lamp GLE which was already closed at contact 43 when the signal lever SGL was movedto its upper east-bound position. The continuous closure of front contact 46 of this slow dropping line repeating relay TGKP however closes an energizing circuit for. the signal indi- "cator "GE which circuit may be traced from the terminal through front contact 46 of this relay TGKP, and through polar contact 41 of the mag-stick relay'TGKS assuming its right-hand positions The operator istherefore informed by the illumination of .indicating lamps GLE and GE, or by suitable other manifestation if some otherform of indicator is employed, that an eastbound signal has been cleared on the actual track layout. '.This manifestation that an east-bound signal has been cleared is in part manifested by the. position assumed by the signal control lever SGILw The picking upof the signal indicating relay TGKP not only causes illumination of the lamps GLE and GE to manifest that a proceed signal is being displayedv or the illumination of the lamps GLE and TE to manifest that the detector track circuit .is occupied but also performs an electric locking. function byopening its back contacts 51 and 65. At open back contact 51 it prevents the switch lever SML, upon being moved to a new position maliciously or otherwise, from causing the relay OCR from picking up. For if relay OCR were picked up it would by opening its back contact 21 open the signal clearing circuit including relays GCS and GC in multiple. Also at'open back contact 65 the relay TGKP prevents a new switch operating circuit being established at one pointisuch circuit however being electrically locked open at open back contact 6| of relay GZ (see Fig. 1B) at the field station.

Let us now assume that the east-bound train approaching the signal 2 passes this signal 2 and in so doing treads upon the detector track circuit and causes deenergization of the track relay T. The dropping of the track relay T causes the signal 2 to assume its stop position, because this signal 2 is controlled in accordance with traffic conditions in advance, and this in turn causes the signal-at-stop relay M to again pick up to re-close its front contacts 38 and 4| and open its back contacts 40 and 4|. The dropping of the detector track relay T also causes closure of its back contacts 50, 5| and 52 as a result of which the back contact closes a new energizing circuit for the coder |20CT, so that this coder remains in continuous operation, the back contact 50 of track relay T closing before the back contact 40 of the signal-at-stop relay M opens. Also, closure of the back contact 52 of the track relay T results in the intermittent closure of an indication circuit traced from the terminal of the field battery BF, back contact 52 of the track relay T, front contact 4| of the relay M, front contact |3 of the relay |20CT, front contact |2 of the coder I5CT, through the winding of the mag-stick relay TGKS, to the common return wire C, to the mid-point of the battery BF. This current of negative polarity causes the polar contacts 42 and picked up in accordance.- with the impulses of current. transmitted from the. field station: to:=the control ofiice through the: back; contact. 52: of the track: relay T. This. intermittent. picking; up of the linerelay TGK. will maintain the slow drop;- ping line repeater relay TGKP in. its energized position continuously as, a; result of. which the track indicator TE. is. energized and rendered active through a. circuit including the front. con-.- tact 46v of the. line repeater: relay and polar contact 41 of the mag-stick relay TGKS assuming its left-hand position. The, signal indicator GE is therefore rendered. inactive, whereas: the detector track indicating lamp; TE is. rendered; active, thereby informing thev operator thatthe Sig:- nal2 has been operated; to itssstop condition and that; the detector track circuit: at; the fieldz station has become and issstill occupied.

As the; train under consideration: now moves beyond the track switch and. allows the: detector: track relay T to. again pick. up the; detector track indicator TE'is rendered. inactive: and. the signal 2 is again cleared as soon as the train gets beyond those track. circuits (not shown), which enter into the control of the signal 2.. Clearingjof the signal 2. will of course causethesignal-at-stop relay M to again be. deenergized resulting in the rendering of the. signal. indicator GEactive;

Let us now assume that there isxa west-bound train approaching the signals: t: and IA and that the operator desires to have this. train enter the side-track of the. passing siding PS or similardiverging route. The. operator. will, or course,.first return his signal. lever SGL to the middle position to cause the return: of the signal; 2: to. its stop condition, resulting; in the re=energization of the relay M and the extinguishment of the in.- dicator lamp GE, it. being understood that. the track switch and switch machinecannot be op e a d. so long as the relay M. assumesxitsdeenergized or retracted position. This; prohibition against opera ion of. the switch machine is by.

reason of locking circuits provided tozpreventthe switch achine SM ng-v one atedunden unsafe conditions. These locking oirouits well: known in the art, have not been specifically: illustrated, but have been shown, conventionally byj'the relay Ii. Movement of the. signal leverSGIl to its:mid.-. dl position will of course put the signal 2. to stop and caues the indicating lamps. and: GE to be extinguished and will. cause the-contact 5:!- of relay TGKP included in the energizing. oircuitaof relay OCR and the contact. 65,: included in the switch control. circuit to: recluse; to allow th oder l5CT to be oscillated and the track switch to be operated in response to movement. otthe lever SML.

Let us' now assume that. the operator in his desire to have the approaching. train enter the side track of thepassingisiding BS. operates his switch lever SML to itsupper; ortaket-s-iding po: sition. Movement of the contact 55,- of the switch lever SML to-its upper position olosesan energizing circuit for the out-ot-ccrrespondence relay OCR- which may betraced from: the terminal of the office battery B0,. through the contact 56 of the mag-stick: relay assuming ts gh positio through contact 55ctt-he.

aesasoc switch control lever-SML, through back contact 51 of the linev repeater'relay through the winding of the. out-of-correspondence relay OCR, to the common return. wire; C connected to. the midpoint. oithe offioe battery BO.. Closure of this circuit causes the out-of-correspondence relay OCR to." assume its energized position resultinthe closure of its front. contacts. 58; and 5.9 and the opening of its. back contact 211:. The closure. of: its front. contact. 53 renders, the; out-ofcorresponclence indicator OCR. active: to inform the operator that an out-of-correspondence condition between his switch. control lever SML and thetrack switch in, the field now exists. The: opening of the back Contact 2'! of this-outof.correspondence relay OGR opens; the. Signal control circuit heretofore traced and including the signal control contact. 26:. The closure of the front contact 58, on the otherhand, of this out? ot-correspondence relay OCR establishes. a differ ener izing circuit. for the coder TSCT. The. closure of this coder circuit, of course causes the coder 156T to intermittently pick upits contacts 1.0 and II! at a substantially 7'5. imp lse per minute rate.

1 With the double-throw contact [0 of'the coder 15CT'now intermittently assuming it raised csiticn and the switch lever assuming its raised position a negative. energizing circuit for the mag-stick relay .WCS, at the field. station is intermittently closed. This circuit. maybe traced from the terminal. through the contact'lill of the switch control. lever back contact 65 of relay TGKB,.front contact ID of the coder T, line wire-WZ-WK, back contact ll of the coder 1210GT (now at IQSQL, through the back contact 6| of the signal control relay GZ, through the winding of the rn ag sticlzrelay WCS, to the commonreturn Wire (6 connected to. the mid-point of the oiiice battery BO Since. the current flowing in this circuit isoi negative polarity the mag-stick relay WCS will be operated to its left-hand position where it will remain in spite of intermittent deenergization of. this. line circuit. This causes its polar contact 62- and 63 to assume the left-hand position. Also, with the polar contact. 62- assuming its left-hand position the lower winding of the neutral line relay WC is intermittently energized since it is connected in multiple with the winding of the mag-stick relay WCS as a result of which the front contact 64 of the neutral line relay WC is intermittently closed, resulting in the intermittent energization of the slow dropping line repeater relay WCP. This repeater relay WCP is suiliciently slow dropping so that:it will not drop. in spite of the intermittent interruption of the switch control circuit including theline wire WZe-WK just traced. The picking up of the line repeater relay WCP, by the opening of its back contact 22, interrupts the stick circuit for the switch control relay WZ thereby causing this relay to. assume its deenergized retracted position.

With the polar contact 63 of the mag-stick relay WCS now assuming its leftehand position the switch control relay WZ is now. energized by current of negative polarity which. flows from the terminal of the field battery BF, through contact 63 of relay WCS assuming its leftehand position, and through front contact 22 of the line repeater relay WCP. This current of negative polarity causes the switch control relay WZ to assume its left-hand energized position .as a result of which the reverse circuit R instead of the normal circuit N for the switchxmachine. SM

stroke the switch indication relay WP is operated is closed. Operation of the'switch control relay WZ to its reverse position breaks the energizing circuit, including contacts l8 and IQ of relay WP and including contacts' l6 and ll of this relay WZ, for the correspondence relay NWP. The circuit for the switch indicating correspondence relay RWP also including these contacts l6 and l! is however notclosed because the contact. is open and the contact 23 will open as soon as the switch machine has been unlocked-for its re- J verse operation. This reverse circuitfor' the switch machine SM may be traced from the tenninal of the field battery BF, front contact 66 of lock relay L, front contact 61 of the relay -WZ, polar contact 68 of this same relay-assuming its left-hand position, the reverse wire R and apparatus of the switch machine SM, through the common return wire C connected to them'idpoint of the field battery BF. The closure of this reverse circuit for the switch machine SM causes this switch machine to unlock as a result of which the switch repeater relay WP assumes its deenergized position causing opening of its front contact IS in the energizing circuit for the. correspondence switch indication. relay The closure of the back contact 10 of the relay .NWP establishes an energizingcircuit for the coder IZOCT, so that this. coder IZUCT causes .interw mittent picking up and dropping of its contacts II and i3. During the operation of the switch machine from its normal to its reverse position the polar contact H will remain in itsright-hand or main track position until the switch machine SM has completed its stroke. During this time current of positive polaritymay flow from the terminal through the polar contact II of the switch repeater relay WP, through front contact of the track relay T, throughfront contact 38 of the signal-at-stop relay through front contact ll of the coder I2DCT, through line wire WZWK, through back contact ill of thecoder 150T, through the winding of the; mag-stick relay WKS, to the common return wire C connected to the mid-point of the field battery BF. Since this current is of positive polarity the polar contacts 5A and 56 of the mag-stick relay WKS will continue to assume their right handposition. This contact 54 of course establishes a circuit through the lower winding of theneutral line relay WK so that this relay WK intermittently closes its front contact 13 to cause the slow dropping line repeater relay WKP tocontinuously assume its attracted position so long as the line circuit just traced is intermittently closed. 7

It should be understood that the circuit through back contact iii of coder 150T and front contact H of coder [260T is closed contemporaneously with the circuit for controlling switch machine SM and including front contact lflof coder. 150T. and back contact H of coder IZDCT. With the line repeater relay WKPnow assuming its energized position its front contacts 14 and T5 are closed thereby establishing a supplemental circuit for the out-of-correspondence' lamp OCE which lamp was already, energized through the front contact 59 of the relay OCR. This supplemental circuit extend through the front contact '55 of this relay WKP. The front contact M of this relay WKP establishes an auxiliary circuit for the out-of-corres'pondence relay OCR. The out-of-correspondence relay OCR is' therefore. maintained energized so long as an indication is received over the switch control and indication circuit WZWK. I

As soon as the switchmachine. SMcompletes its to its left-hand'position in which position its polar contact applies negative polarity instead of positive polarity to the mag-stick relay WKS. Operation of contact. 56 of relay WKSv to the left results in opening of the pick-up circuit for outof-correspondence relay OCR." A short time after relay WP assumes its energized position its slow acting repeater correspondence relay. RWP also assumes its'energized position as a result of which its backrcontact 12 is opened, thereby preventing the operation of :the coder IZUCT, and thereby discontinuing the transmission of an indication from thelfield'to the central office over the line circuit: WZ1WK, that.is," insofar as the condition'o'fthe track switchSW and'its-switch machinefSM'is concerned. Upon discontinuance of this transmission of an indication from the switch machine to the central ofilce the relays WK and WK? will of course be both continuously deenergized,"there:by causingth'e opening of contacts 'M and 15 of the line 'repeater relay WKP resulting in the deenergization of the out-of-correspondence rela OCR. Since the relays WKP and OCR are now both'deenergized, and with their respective contacts and 59 open, the out-ofcorre'spondence lamp OCE is extinguished informing the operator not only that the polar contacts .H of relay WP have been operated to the left but also" that'back contacts 10 or 12 of relays NWP and RWP, respectively, have been opened. This signifies to the operator that theswitch machinejSM and itsiassociated track switch SW assume the same positionzas does'the switch control=lever 'SML in the control office.

The switch indication circuit heretofore traced and starting at'the contact II of the switch indication relay WP also included the front contact 5| of the track 'relay' T. In-the event a train should get beyond the insulating joints 9 at one end of the detector track circuit before the switch machine SM has had an opportunity to complete its stroke and reenergize its repeater relay WP the switch indication circuit would include the [back contact T! of the switch repeater relay WP and the'lback contact-5l of the detectorv track relay T.v It maybe pointed out that the switch machine control circuits in the system disclosed areso organized, as well known in'the art, as to permit completion of the stroke of the switch machine' if such'switch machine is initiated while allow continued energization and operation of the switch machineuntil its stroke has been completed. Since the feature of completing the stroke of the switch machine under the conditions assumed. above is well known in the art the specific circuits'for performing this function have not been shown. In this connection it should be observed that'the system of the present invention permits out-of-correspon-dence an dtrack occupancy indications to be transmitted independently and simultaneously as conditions require. This is made possible' because these indications are transmitted over different line circuits.

' 'Since'the operator desires to allow the westbound train to. proceed onto the side track, or a diverging track, as is now possible with the track switch SW assuming its reverse position, the operator will operate his signal lever SGL to its lower'orwest-b'ound position. With the contact 25 0f the signal leverSGL assuming its lower position an'en'ergi'zing circuit ifiOr the coder .150! is 1close'd through its interrupter contactbll to cause intermittent .energ-iz'ation of this coder 150T, Ji 's'dlting in intermittent rlift'in'g tand dropzping (if its ccntacts l'lland i2. With the contact.

Elli

of the office battery B0. The intermittent-"com pletion of thisxcircuit lb-yithe intermittent closure of back contact 12 of coder 150T causes inter"- mittent current pulses of negative polarity "to flow through the winding of the 'maigestick relay GCS causing 'operatien of asp-om contact 28 to the left-hand position where they will remain continuously to'est'ablishia ci'rf'cuit fer the -.neutral line relay GC including this contact 28 and bridged across the winding of the mag-stick r'elay GCS. The -net'res-ult is that-the neutral line relay GC intermittently closes'its front contact 2-9 in response to the impulses transmitted aim causes continuous closure of frcnticonta'ctlifl' cf the line repeater rela 'GCP 'which latter relay is controlled through this co'ntact 29.

With the'polar contacts "or the relayGCS assuming the left hand positioni'andwith :the front contact 30 of the line repeater relay'GCP :cldsed a circuitfor the signal ccnt-rol :re'lay GZ Eior energizing this relay with current of negative polarity is closed t'cTesultinthtiimeraition of this signal control relay GZ to its left harfd eriergizeii position.

With the signal "control relay GZ energized :to its left-hand position and with "the switch repeat- 'r relay WP energized to its 'left h'and position an energizing circuit conventionally illustrated by 'a dotted line *3! tier the mechanism "on the take-siding signal [A is closed. The closure of this circuit causes the takesiding si'g'nal l A to indicate proceed in response "to which the approaching West-bound cram 'may enter the side track 'or' diverging lrou'te over which this signal |A"governs trafiic. ilhis'circiiitiillusiii'ated in part by dotted line :31 includes front contact '48 of the switch correspondence relay but does :not include a trafiic controlled (contact .X because the side track of the ipassing-sidingis 'assumed :not to be track circuited'. Attention is directed to the fact that a back -contacttl of the signal control relay G2 is included :in "the control circuit for controlling the switch machine 'SM through the medium of the line wire W'Z- WK. Thisprovision is made to prevent a switch 'control being transmitted from the central offie to the .field station while the signal control relay GZ is -:energized. This serves :as an additional *check against the operation of the switch machine while a signal-clear .control is transmitted to the field stationwhich might result in the :clearing of a signal. It 'is'of course understood that in "practice the switch'ma-chine SM could not beoperated unless the signal at-stop relay M were then in its attracted position. The contact 6] therefore may be effective before the relay M-has had time to respond. Attention is also directed tothe back contact 51 of the relay FIGKP :(Fi'g. =l'A) rincludedin the energizing circuitfor the put-of-corre- 'spbndence relayOCR. This feature prevents an 'out fof corres'pondence indication 'being'given if the switch control lever SML is operated while an indication 'signifying a proceed signal indicahon in the field or a track :o'ccupancy indication 'is given. 111; 'also prevents operation of the coder 715(3'1 in response to an out-of correspondence condition "of the switch machine control lever SM'L faznd the ma'g 'stick indication 'relay WKS. It also prevents picking up of the relay OCR by qn'cvement of the switch control lever SML during .a signal clearing condition, which is desir'- 'iible, for otherwise :a "clear signal could be put to swp by 'opei atioii ofthis switch control'flever. In this connectionv attention is directed to the back contact -25 of relay OCR included in the signal clearing circuit.

Another electric interlocking feature consists in the provision of the back contact 65 of the relay TGKP included in the switch control circuit. This contact "65 prevents a switch control beingtransmitt'ed to the field station while either a track occupancyor a signal-clear indication is being received. This :is desirable for even though operaticn of the track switch SW is prevented by ldcaliinterlocking and approach locking contacts, such-as by the contact 65 of the lock relay L, wider the assuined condition, it is desirable not totransmita new switch control to the field station when either an OS indication or a signal-at-proceed indication is being received.

Gfaphs Fig. '2.-In'the foregoing part of the specification it has been generally stated that the *control circuits and the indication circuits over the line wires WZWK and GZ-GK-TK are closed and energized intermittently and at times contemporaneously. In order to more clearly point out what the nature of this interinittentfclosure d'f various circuits is, Fig. 2 has been added to illustrate how the various circuits including a single line circuit are controlled 'in b'eat frequency fashion. Referring to Fig. '2 of thejdr'awings the numbers starting at zero and ending {at seven shown in the top line and designated SEC denote time'from left to right in seconds. lnhtherwords, in moving from left to rightj'o'ver -Fig. 2':o'f the drawings it must be asshined that time passes inseconds as signified by these numbers. The "first graph designated TBCTG signifies the action of the contacts of coder T'ECTascOnipared with the passing of time. E'al'cli cf the top lobes or waves of this curve designate that front contacts Ill and 12 of coder 15CT are closed whereas the valleys in this curve designate that back contacts I0, l2 (and M of this code'r '15CT are closed. If each of these lobes and' vall'eys is considered to be a cycle, as is the case, it -willbe "seen that 7 /2 cycles elapse during the first "sin seconds of the lapse of time, or in other "words, the coder 15CT operates at a '75 energization's and deen'ergizations per minute rate. Similarly,"thesecorid graph IZOCTG signi fies thatiithis coder IZOCT 'picks up and drops away times a minute. This is evident from the fact that two complete cycles'exist for each second of the lapse of time. Referring to Figs. 1A and 1B 'of the drawings it will be seen that the line circuit comprising ilin'e wire WZWK and common return wire 0 may be completed in namely circuit 2 includes back "contact ID of culier l5G-Tand frontzcontact ll of coder IZUCT,

of which the third circuit includes the relays at both the control office and the field station in series and passes through back contacts Ill of coder 150T and back contact H of coder l2llCT, and of which the fourth circuit includes the sources of current at both the central oflice and the field station in series and which includes front contact IU of coder 150T and front contact ll of coder I20 CT. The intermittent connecting of the batteries in series is not considered harmful in view of the appreciable line resistances involved. The intermittent closure of these four different circuits have been illustrated graphically in Fig. 2 of the drawings by waves in graphs C (circuit I); C (circuit 2); CR (relays in series) and CB (batteries in series).

By referring to these four graphs illustrated in Fig. 2 of the drawings it will be seen that one of these four circuits is closed at-all times, and that at no time are two of these circuits closed simultaneously. In other words, these four circuits are so closed in sequence that one of the circuits is closed at all times and it will be seen from these graphs that each of the circuits isclosed intermittently without appreciable gaps of open circuit condition between successive closures.

Nothing has been stated hereinbefore in regard to the putting of a signal to stop after a signal has been cleared, but it is readily understoodthat movement of the signal lever SGL to its intermediate position from an extreme position 'will result in the deenergization of the repeating neutral line relay GOP and the opening of its contact 3|} which will result in deenergization of the signal control relay'GZ and the placing of the particular signal which was then clear into its stop condition. v

Having thus shown and described one rather specific embodiment of applicants invention it should be understood that the specific structure said field station, control means for connectingat a sufficiently rapid rate and for periods of suflicient durations that a substantially continuous control consisting of a series of current impulses and a substantially continuous indication consisting of a series of current impulses to efiectively control said control relay and said indication relay respectively may be transmitted in opposite directions over said line circuit contemporaneously, and means for rendering the electroresponsive means at the controlled end active when an indication is to be transmitted from that end 1 2. In a centralized trafiic controlling system of the unit line wire type for railroads, in combination with a line circuit connecting a central ofiice and a distant field station, a control source of current and an indication relay at said ofiice, an indicatio'n source of current and a control relay at necting said indication source to a field branch illustrated has been selected to facilitate the description of applicants invention and its mode of operation in order that the underlying principles of applicants invention may be understood and should not be considered as a showing of all forms the invention may take nor in a limiting sense, and it is further desired to be understood that various changes, modifications, and additions to the specific structure illustrated may be made without departing from the spirit or scope of the invention so long as these changes come within the scope of the appended claims.

What I claim as new is: v

1. In a centralized trafiic controlling system of the unit line wire type for railroads, in combination with a line circuit connecting a central ofiice and a distant field station, a control source of current and an indication relay at said ofiice, an

indication source of current and a control relay at said field station, control means for connecting said control source to an office branch wire or leaving it disconnected, indication means for connecting said indication source to a field branch I wire or leaving itdisconnected, normally at rest oscillatory contacts one at said oifice and one at wire or leaving it disconnected, normally inactive oscillatory contacts one at said office and one at said field station for when active alternately connecting the associated source and branch wire and the associated relay into said line circuit and when inactive connecting only the associated relay into said line circuit, means for operating said oscillatory contacts at frequencies such that if both of said oscillator contacts are active the beat-frequency of the two oscillatory contact frequencies is high enough to avoid long periods of synchronism conditions so that two-way transmission over said line circuit is effective, and

means for rendering the oscillatory contacts at that end of said line circuit from which a control or an indication is transmitted active and for automatically rendering it inactive when the apparatus to be controlled has responded.

3. In a centralized traffic controlling system for railroads of the unit line wire type comprising, a line circuit connecting a central oflice and a distant field station, a control source of current and'an indication relay at said office, an indication source of current anda control relay at said field station, control means for connecting said control source of a particular polarity to an office branch Wire or leaving it disconnected, indication means for connecting said indication source to a field branch wire or leaving it disconnected, oscillatory contacts one at said oflice and one at said field station each when operated alternately connecting the associated source and branch wire and the associated relay into said line circuit but normally inactive and when inactive connecting the associated relay into said line circuit, said oscillatory contacts being normally inactive and when both active operating at different rates such that both a control circuit and an indication circuit are intermittently established at sufiiciently rapid rates which circuits are maintained for sufiicient durations that a substantially continuous control channel and a substantially continuous indication channel over which to control said relays are established over said line circuit contemporaneously, and means for operating the oscillatory contacts at either or both ends and when operating them at one end only then operating them at that end from which a control or indication is transmitted and only when such control or indication is being transmitted.

fl. In a centralized trafiic controlling system for railroads of the unit line wire type comprising, a line circuit connecting a central office and a distant field station; a control source of current and an indication relay at said office, an indication source of current and a control relay at said field,

station, control means for connecting said control source to an oiiice branch wire Or leaving it disconnected, indication means for connecting a particular polarity terminal of said indication source to a field branch wire or leaving it disconnected, normally inactive oscillatory contacts one at said office and one at said field station each when active alternately connecting the associated source and branch wire and'the associated relay into said line circuit, means for operating said oscillatory contacts at either or bothends and operating them at different rates such that when both are operated at the same time both a control circuit and an indication circuit are in-- termittently established at sufiiciently rapid rates and for periods of time long enough such that if both of said oscillatory contacts are active a sub stantially continuous control channel and a substantially continuous indication channel circuit contemporaneously, and means for rendering the means for operating the oscillatory contact at the office active when a control is to be transmitted and rendering the means for operating the oscillatory contact at the field station active when an indication is to be transmitted and for at times rendering both of said last mentioned means active contemporaneously.

In a centralized trafiic controlling system for railroads of the unit line wire type comprising; a line circuit connecting a central office anda distant field station, a control source of current and a polar indication relay at said office, an indication source of current and a polar control relay at said field station, control means for connectingsaid control source of a particularpolarity to an ofiice branch wire or leaving it disconnected, indication means for connecting a particular polarity terminal of said indication source to afield branch wire or leaving it disconnected, normally inactive oscillatory contacts one at said office and one at said field station each when active alternately connecting the associated source and branch wire and the associated relay into said line circuit and when inactive connecting the associated relay into said line circuit, said oscillatory contacts when both active operating at difierent' rates such that both a" control circuit and an indication circuit are intermittently established at sufliciently rapid rates and for periods'of time long enough such that a substantially continuous control channel and a substantially continuous indication channel are established in opposite directions over said line circuitcontemporaneously,

electro-responsive means for each oscillatory contact to oscillate the same, and means for rendering the electro-responsive means at said central oflice active when said control means is operatedior rendering the electro-responsive means at said field station active when said indication means is'operated and for rendering both of said electro-responsive means active when the control means and indication means are both operated. i

6. In a centralized traffic controlling system for railroads, the combination with a central ofllce and a distant field station, a power operated track switch at said field station; a line circuit connecting said ofiice and-field station, a control lever for controlling said track switch through the medium of said line circuit, a correspondence relay at said oflice having an energizing circuit are established in opposite directions over said line closed: if said lever. and: said track switch assume non-correspondencev positions, an indication relay at said ofii'ce' and controlled: over said line circuit and. energized" so long as anindication of the position assumed by the. track switch is: transmittedlfro-m said fieldstation to said oifice, means fon' transmitting from said fieldstation tosaid office? the: position assumed by said track switch while in) transit and for a" short time thereafter, and-an: auxiliary energizing circuit for said correspondencerelay including a front contact-of said indication. relay.

7. In a system for transmitting controls in oppositeldirectionsover a single line' circuit comprising, a line circuit connecting a first station and a second station, a first control means inoludin'g a control: source and a second electroresponsive' means at said first station, a second control means including a control source and a first electroeresponsive means at said second station, normally inactive oscillatory contacts at eachofsaid stations which when rendered active alternately connect the control source and the electro-resp'onsive means at that station to the linev circuit and wheniinactive connect only such electro-responsive means, to such line circuit, meansxat'said' first station for at times rendering both said first control means and the oscillatory contacts at-suchfirst station active, means at said. second station for at times rendering both said second control: means and the oscillatory contact at such second station active, said? oscillatorycontacts each when active alternately connecting the associated: source and the associated electro-responsive means into said line circuit and operate at different rates such that if both oscillatory contacts are simultaneously active control circuits in both directions over said line circuit:arerintermittently established each control means transmitting successive impulses. of ourrent at asufliciently'rapid rate with the impulses extending for sufficient durations of time that a substantially continuous control is transmitted in both directions over said line circuit contemporaneously, and means at one of said stations for rendering. the oscillatory contacts at such station active when a control or anindication is transmitted from that station and for rendering them automatically inactive when the apparatus to be controlled has responded;

8.- In a centralizedtrafiiccontrolling system of the unit line wire type for railroads, in combination with a line circuit connecting a central office and a distant field station, a control source of current and an indication relay at said ofiice, an indication source of current and a control relay at said field station, control means for connecting said controlsource to an ofiice branch wire or leaving it disconnected, indication means for connecting said indication source to afield branch wire orv leaving it disconnected, normally inactive oscillatory contacts one at said office and one at said'field station for when active alternately connecting the associated source and branch wire andthe associated relay into said line circuit and when inactive connecting only the associated relay into said'linecircuit, electro-responsive means for" each oscillatory contact for operating said oscillatory contacts at'frequencies such that if both of: said oscillator contacts are active the beat-frequency of the two oscillatory contact frequencies is high enough. to'avoid long periods of synchronism conditions so that two-way transmission over said line circuit is effective, and

means for rendering the electro-responsive means at that end of said line circuit from which a control or an indication is transmitted active and rendering both of said electro-responsive means active when both a control and an indication is to be transmitted contemporaneously.

9. In a centralized traffic controlling system for railroads, the combination with a central office, a line circuit extending from said central oifice, a switch control lever and switch indication means at said office, a double-throw contact connected to the office end of said line circuit, electro-magnetic means for alternately and intermittently connecting said line circuit to said switch control lever andsaid switch indication means, a relay for when in an energized condition rendering said electro-magnetic means active, a first circuit for said relay closed only when said switch control lever and said switch indication means assume non-correspondence positions, and a second circuit for said relay closed when said switch indication means is in its active condition.

10. In a centralized traffic controlling system for railroads, the combination with a central office, a line circuit extending from said central ofiice, a switch control lever and switch indication means at said oflice, a double-throw contact connected to the o-fiice end of said line circuit, electro-magnetic means for alternately and intermittently connecting said line circuit to said switch control lever and said switch indication means, and means for rendering said electro-magnetic means active effective when said switch control lever and said switch indication means assume non-correspondence positions and also effective while a switch position indication is being received over said line circuit irrespective of whether or not the received indication is in agreement with the position then assumed by said switch control lever.

11. In a centralized traflic controlling system, the combination with a central oflice and a field station, of two line wires connecting said office and field station, a control source and a plurality of indication relays at said office, an indication source and a plurality of control relays at said field station, control means for connecting said control source to one, the other, or both of two oifice branch wires, indication means for connecting said indication source to one, the other, or both of two field branch wires, normally inactive oscillatory contacts two at the ofi'ice end and two at the field station end of said line wires for when active alternately connecting the associated branch wire and the associated-relay to each of said line wire ends and when inactive connecting only the associated relay to its line 

